1. Technical Field of the Invention
The present invention generally relates to communication networks. More particularly, and not by way of any limitation, the present invention is directed to a remote access link fault indication mechanism operable with an Ethernet OAM network.
2. Description of Related Art
In order to adapt the well known Ethernet technology in a carrier-grade service environment, various standards are being developed that aim to provide advanced operations, administration and maintenance (OAM) capabilities (also referred to as Ethernet Connectivity and Fault Management or Ethernet CFM) across the entire network from one end to the other end. Since the end-to-end service network environment is typically comprised of a patchwork of diverse component networks (e.g., metro access networks and core networks using a variety of technologies) that may belong to different organizations, network operators and service providers, the Ethernet OAM plane is envisioned as a hierarchically layered domain space wherein specific OAM domains are defined corresponding to the constituent network infrastructure and provisioning. In particular, two standards, IEEE 802.1ag and ITU-T (Question 3, Study Group 13), incorporated by reference herein, that are specifically concerned with end-to-end Ethernet OAM define a customer-level domain at the highest level of hierarchy, which comprises one or more provider domains (occupying an intermediate level), each of which in turn includes one or more operator domains disposed at a lower hierarchical level. By way of standardization, the OAM domain space may be partitioned into up to a number of levels, e.g., 8 levels, each domain corresponding to a particular level, wherein a domain is defined in terms of what are referred to as flow points. In the context of the IEEE 802 specification suite, the flow points are new entities contained in Media Access Control (MAC) “interfaces” and “ports” as defined in related standards documentation. A flow point at the edge of an OAM domain is called a “Maintenance End Point” or MEP. A flow point inside a domain and visible to a MEP is called a “Maintenance Intermediate Point” or MIP. Whereas MEP nodes are used by system administrators to initiate and monitor OAM activity (by issuing appropriate OAM frames), MIP nodes passively receive and respond to OAM flows initiated by MEP nodes. An OAM domain having one or more MIP nodes is bounded by two or more MEP nodes, wherein a “Maintenance Entity” (ME) is defined to include a set of MIP nodes disposed between one MEP node and another MEP node. Thus it is possible to have more than one ME in a particular OAM domain.
Although the Ethernet OAM architecture as currently being standardized provides an impressive framework for addressing end-to-end Ethernet Connectivity and Fault Management at any level of the OAM hierarchy, a number of issues remain to be solved. Of particular concern is the scenario where customers are reluctant to implement the IEEE 802.1ag OAM technology due to cost considerations. Since the access links that couple customer network sites to a metro provider network typically belong to the customer, customer networks as well as the access link technology used may operate in a non-802.1ag environment whereas the metro provider network may comprise an 802.1ag-compliant network. One example of a non-802.1ag environment is a network environment operating according to the IEEE 802.3ah standard. In such a situation, accordingly, a need arises with respect to providing a remote access link fault indication mechanism based on interworking functionality so that a local customer site may be alerted appropriately.